Barring major technological changes in available processes, projected expansion of energy production will utilize substantially increased quantities of water. In many areas of the country, planning will be needed to accommodate new energy-related water demands. As a basis for planning, projections of water allocation and demand for energy production will be needed to identify the extent with which increased energy production will compete with other uses for available water. In particular, this report discusses the development and application of a multi period, multi plant linear programming model of an energy production system and associated water supply components. The model simultaneously appraises alternative expansion strategies and operating schedules for steam-electric power generation and coal gasification industries. The model identifies the type, size, location, and sequence of construction of new energy production facilities; and the levels of energy production and transmission that minimize the costs of meeting demands for electricity and gas over a specified future time period. For each minimum-cost expansion strategy that is identified, the model a1 so determines corresponding information about the amount, location, and sequence with which water will be used in future energy production. This information is, in effect, a spatially disaggregated projection of the a1 location and demand for energy-related uses of water. The model was implemented using the state of Illinois as a case study region. The results from this application indicate that projected gross withdrawals of water for steam-electric power generation will decline while consumptive demands for this use will increase. Spatially, future patterns of water use for power generation are likely to be more evenly distributed throughout the state. The development of a coal gasification industry in Illinois is likely to bring about a sizeable increase in future energy-related water demands.